<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
function initEven() {
    var footballs = document.getElementById("football"); //取id费football的标签
    var lis = footballs.getElementsByTagName("li"); //取name为li 的标签
    for (var i =0; i < lis.length; i++) { //遍历
    var li = lis[i];
    li.onmouseover =function() { //当鼠标移动到某个li上时执行
        var footballs = document.getElementById("football"); 
        var lis = footballs.getElementsByTagName("li");
        for (var i =0; i < lis.length; i++) { //遍历
        var li = lis[i];
            if (li ==this) {
            li.style.background ="red"; //将当前的背景设为红色
                li.onclick =function() { //当点击是将字体设为30号
                    this.style.fontSize =30 + 'px';
                }
            }
        else {
                li.style.background ="white"; //将其余的背景设为白色
                li.style.fontSize =18 + 'px'; //将其余的字体设为18号
            }
        }
    }
        li.onclick =function() {
                this.style.fontSize =30 + 'px';
        }
    }
}
</script>
</head>
<body onload="initEven()">
    <ul id="football">
        <li>曼联</li>
        <li>中国</li>
        <li>美国</li>
        <li>阿根廷</li>
        <li>西班牙</li>
    </ul>
</body>
</html>